Dryer apparatus with light controlled variable speed tumbling drum



Dec. 1 5, 1979 J. w. JACOBS DRYER APPARATUS WITH LIGHT CONTROLLED VARIAB SPEED TUMBLING DRUM 2 Sheets-Sheet 1 Filed May 27, 1969 ATTO R NEY 3,546,786 IABLE J. W. JACOBS Dec. 15, 197@ DRYER APPARATUS WITH LIGHT CONTROLLED VAR SPEED TUMBLING DRUM 2 Sheets-Sheet 2 Filed May 27, 1969 I TIMEQVHNUTES) w w m w m m Qi 9 5% 23% ATTORNE Y nited States atent 3,546,786 DRYER APPARATUS WITH LIGHT CONTROLLED VARIABLE SPEED TUMBLIN G DRUM James W. Jacobs, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed May 27, 1969, Ser. No. 828,129 Int. Cl. F26b 13/00 US. Cl. 34-52 Claims ABSTRACT OF THE DISCLOSURE In preferred form a clothes dryer having a horizontal cylindrical drum rotated at a variable speed in response to the tumbling action of clothes within the drum which action is sensed by photoelectric means. A light beam is axially directed through aligned circles of holes in both ends of the drum and is received by a light dependent resistor which is located adjacent the opposite end of the drum. A control circuit including the light dependent resistor and a magnetic slip clutch effects rotation of the tumbling drum at a speed proportional to the strength of the light signal received by the resistor. When clothes plaster against the cylindrical surface of the rotating drum which condition is partially caused by excessive drum speed, the light beam is interrupted and is not received by the light dependent resistor. This interruption of the light beam alters the light dependent resistor and the control circuit to reduce the rotational speed of the drum which reestablishes desirable tumbling action of the clothes.

This invention relates to clothes dryers having a horizontal rotatable drum for tumbling clothes and more particularly to such a dryer whose drum speed is controlled by a photosensitive device which senses the tumbling action of clothes within the drum.

Experience with conventional dryers of the type having horizontal drums to tumble clothes indicates that a rotation of approximately 50 revolutions per minute will produce desirable tumbling action of clothes under normal conditions. Desirable tumbling action occurs when the damp clothes are carried against the cyindrical surface of the drum by its rotation until they flutter downward toward the bottom of the drum in free falling movement. However, factors such as degree of dampness, the build up of static electricity within the clothes and the kind of materials which are tumbled may cause the clothes mass to plaster against the Outer cylindrical surface of the rotating drum. Plastering of the clothes mass is undesirable and will greatly increase the drying time.

Once clothes have begun to plaster against the drum, its speed must be reduced to cause the clothes mass to break away from the drum and begin desirable tumbling action.

The rotational speed of the tumbling drum in the present invention is varied to produce desired tumbling action of the clothes by applying a variable current to a magnetic slip clutch imposed between the drive motor and the drum. The magnetic slip clutch transmits rotation to the drum at speeds which are varied in response to the variable current supplied to the clutch coils.

A photosensitive resistor in a transistorized circuit is utilized to vary the current input to the slip clutch coils. More particularly, a light source located near one end of the rotating drum shines through holes in the drum to provide a beam of light through the drum. The light beam extends axially through the drum in a path adjacent to the drums inner cylindrical surface. During normal tumbling action the light beam passes through the drum and strikes the photosensitive device. This causes the transistorized circuit to supply full current strength to the clutch coils for driving the drum at maximum speed. When damp clothes are plastered against the drum, the light beam is blocked and the photosensitive resistor alters the current output from the transistor circuit to the clutch coils and consequently reduces the speed of drum rotation.

Therefore, an object of the invention is to provide a clothes dryer of the type having a rotating horizontal drum for tunmbling clothes therein which utilizes photosensitive means to sense an undesirable plastering of clothes against the drum and to reduce the rotational speed of the drum to establish desirable tumbling action of clothes.

A further object of the invention is to provide circuit means for a clothes dryer including a photosensitive resistor which detects improper plastering of clothes against the dryers rotating drum and reduces the rotational speed of the drum to establish desirable tumbling action of clothes.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIG. 1 is afront view partially in section of a clothes dryer suitable for use with the present invention;

FIG. 2 is a fragmentary top view of the dryer taken along section line 22 of FIG. 1 looking in the direction of the arrrows and partially broken away to reveal the drum interior;

FIG. 3 is a side view of a dryer taken along section line 3-3 of FIG. 1 looking in the direction of the arrows and partially broken away to reveal the drum interior;

FIG. 4 is a speed control circuit diagram showing the photosensitive resistor of the present invention in a transistorized circuit; and

FIG. 5 is a graph plotting drum speed vs. time of the subject clothes dryer.

In FIG. 1 of the drawings, a domestic dryer 10 is illustrated including an outer case 12 having a top wall 14, side walls 16 and 18, a rear wall 20 and a front wall 22. A cylindrical tumbling drum 24 having a rear end portion 26 is located within the interior of casing 12.

A central rearwardly protruding shaft 28 formed on end wall 26 is supported for rotation by a rear bulkhead 30 which is vertically secured between top 14 and side wall, 16, 18. A front end 32 of tumbling drum 24 has an outwardly directed annular flange 34 thereon which is concentrically postioned within an annular flange portion 36 formed on an access opening collar 38 which is attached to the front wall 22. A plurality of bearing elements 39 are located between flange 34 and flange 36 to support the front end of the tumbling drum 24 for rotation. Flange 34 and collar 38 define an access opening 40 into an interior 42 of drum 24 which opening is closeable by a door 44 pivotally secured to front wall 22.

In the illustrated arrangement of the dryer in FIGS. 1-3 a control panel 46 is located on the top 14 adjacent the rear wall 20 for mounting control apparatus which directs dryer operation.

Tumbling drum 24 is rotated about a horizontal axis within dryer 10 by an electric motor 48 supported within casing 12. Magnetic slip clutch 50 is interposed between the motor 48 and a drive shaft 52 for transmitting rotation of the motor 48 to tumbling drum 24 through a drive belt 54. Belt 54 extends around the drive shaft 52 and the cylindrical tumbling drum 24. A suitable magnetic slip clutch for use in the present invention is discolsed in US. Pat. No. 3,328,983 issued July 4, 1967 to Brucken et al.

Belt 54 maintained in tension by a slack take-up mechanism which includes an arm 56 pivotally connected at one end to a bracket 58 of motor 48 and supporting a shaft 60 at the other end. Shaft 60 supports a roller 62 which laterally bears against belt 54 to maintain the belt in tension. A spring 64 which extends between motor 48 and arm 56 bears roller 62 laterally against belt 54.

Damp clothes within the interior 42 of the drum are dried by heated air which is forced through drum 24. More particularly, ambient air is drawn into an inlet 66 located near the back side Wall 16 and passes through an electrical resistance heater 68 which increases the temperature of the air. Air fiows from heater 68 into a space 70 located between the rear bulkhead 30 and end wall 26 of drum 24. A seal 72 between bulkhead 30 and end wall 26 prevents escape of air from space 70. Heated air passes from space 70 through a plurality of openings 74 within end )wall 26 into interior space 42 where it contacts damp clothes. Subsequently, air passes from interior space 42 into a fan inlet 76 which extends from space 42 to a fan 78 which is driven by an electric motor 80. From fan 78 air is discharged from the dryer through an exhaust duct 82.

Past experience with clothes dryers has revealed that a drum speed of 50 rpm. will produce desirable tumbling action of damp clothes within a conventional size drum. Desirable tumbling action occurs when clothes break away from the cylindrical surface of the horizontal drum before reaching the apex of their rotation within the drum and shutter downward through the central region of the drum.

A number of factors however may influence the damp clothes to plaster against the cylindrical surface of the drum. This prevents maximum exposure of the clothes to the heated flow air through the central region of the drum. Three significant factors which have a propensity to cause plastering of the clothes mass against the cylindrical surface of the drum are static electricity, the affinity of some materials for others and the degree of dampness of the clothes mass.

The present invention utilizes photoelectric sensing means to detect a plastered condition of clothes against the outer Wall of the rotating drum and to reduce the speed of the drum to establish desirable tumbling action within the drum. More particularly, a light source 84 is mounted upon a front bulkhead 85 for directing light through a ring of ports 86 within the front end 32 of the tumbling drum 24. Ports 86 are located in a circular path concentric to the rotational axis of drum 24 and adjacent the drums cylindrical surface. This produces a light beam which extends from port 86 through the tumbling drum 24 and through a ring of ports 88 in the rear end wall 26 of tumbling drum 24. Ports 88, like ports 86, are located in a circular path concentric to the rotational axis of rotating drum 24. In addition, ports 88 are axially aligned with ports 86 to permit the light beam to extend intermittantly through the drum 24 as it rotates. This light beam strikes a photosensitive device 90 after passing through drum 42.

Normal counterclockwise rotation of drum 24 is indicated by dotted lines in FIG. 1 of the drawing. During normal dryer operation, clothes within drum 24 are held against the cylindrical surface of drum 24 by centn'fugal force until approaching the top of the rotating drum 24. Upon reaching this point it is desirable for the clothes to separate from the drum 24 and begin to flutter downward through the central region of the drum. This tumbling action provides maximum contact between the clothes and the heated air flowing through the drum.

While clothes undergo desirable tumbling action, the aforementioned light beam which extends from source 84 to the photosensitive device 90 is uninterrupted as it passes through the drum. However, when damp clothes plaster against the rotating drum 24 and consequently do not flutter through the dru'ms central region, the light beam is interrupted and does not strike the photosensitive device 90.

A drum speed control circuit for use in the above described clothes dryer is illustrated in FIG. 4. A motor energization circuit extends from L1 through a conductor 92, and on-off switch 94, conductors 96, 98, 100, 102, through motor 48, conductors 104, 106, 108, and 112 to L2. On-oif switch 94 is controlled by a conventional timing mechanism 114 connected across L1 and L2 by conductors 116 and 118.

A light energization circuit extends from L1 through conductor 92, through switch 94, through conductors 96, 98, 120, through light '84, through conductors 122, 108, 110 and 112 to L2.

A magnetic slip clutch energization circuit for clutch coil 124 is shown in FIG. 4. This circuit includes a step transformer 128 which has a primary coil 130 with one end connected to L1 through conductor 92, on-oif switch 94, conductor 96 and conductor 132. The opposite end of primary coil 130 is connected to L2 through conductors 112, 110 and 134. An optional manually actuated switch 133 is inserted in line 132 to permit a no tumble election for delicate fabrics. A secondary coil 136 of the transformer 128 is center tapped by a conductor 138. The end leads of secondary coil 136 are connected to conductors 140, 142, respectively, through diodes 144, 146 for producing full wave rectification of the'transformer power input. This produces a direct-current potential across conductors 148 and 150 and is the source of power to the clutch energization circuit. A capacitor 152 is connected across the conductors 148, 150 to filter out AC pulses from the DC supply.

The aforementioned photosensitive device 90, more particularly may be a light dependent resistor, or LDR, having a high dark resistance and a decreasing resistance in the presence of light. Typically, such units are made of cadmium sulfide, or cadmium selenite. One terminal of LDR 90 is connected to conductor 150 which receives DC power from secondary coil 136. The other terminal of LDR 90 is connected through conductor 154 and resistor 156 to the base of a control transistor 158. The emitter of transistor 158 is connected by conductors 160, 148 and 138 to the secondary coil center top. The collector of transistor 158 is connected by conductor 162 to the base of a power supply transistor 164. The power supply transistor 164 which is triggered by transistor 158, controls the energization of the magnetic clutch coil 124 of slip clutch 50.

More particularly, the circuit for energizing coil 124 extends from conductor 150 through coil 124, through a conductor 166 to the emitter of power supply transistor 164. The collector of the transistor 164 is electrically connected through conductor 168 and a resistor 170 to conductor 148. When the power supply transistor 164 is conductive, a noncyclic DC. current of a predetermined value will flow through the transistor 164 from the conductor 150 to the conductor 148 to produce a predetermined maximum energization of coil 124 of slip clutch 50.

A desirable feature of the illustrated circuit is the voltage dividing resistor 170 between conductors 168 and 148 that produces a potential across resistor 172. Resistor 172 is connected between the conductor 168 and the base of control transistor 158. The resistor 170 is of a small enough magnitude so as not to appreciably reduce the current flow through the coil 124 when it is energized. Its resistance is sufficient, however, to produce a voltage differential across the resistor 172 which causes a small current to flow to the base of control transistor 158. As current through transistor 164 is increased the current through the resistor 172 is also increased. This produces an effective amplification of the control signal to the base of transistor 158 for regulating the conductivity of the transistor 158. By this means the pair of transistors 158, 164 are made more sensitive to the changes in resistance of LDR 90.

"From the above description it can be readily understood that when damp clothes are tumbling in the drum 24, LDR 90 receives a substantially continuous beam of light from light source 84 through the drum. When LDR 90 is in a low resistance state which occurs when it is receiving the light beam a predetermined maximum potential is applied across the base and emitter of control transistor 158. This triggers transistor 164 and causes a large current to flow between conductor 150 and conductor 148 through clutch coil 124, conductor 166, transistors 164 and 158 and conductors 168, 160. During this maximum current flow through coil 124, slip clutch 50 transfers a maximum rotational speed from motor 58 to tumbling drum 124 through belt drive 54.

When clothes plaster against the tumbling drum 24 the light beam through the drum is interrupted and does not fall upon LDR 90. Because LDR 90 has a high dark resistance, the voltage potential between conductors 150 and 148 is divided across LDR 90 and the control transistor 158. This decrease in voltage across the base and emitter of control transistor 158 reduces or terminates the flow of current through the power supply transistor 164. Consequently coil 124 is partially or fully deenergized. This deenergization of coil 124 induces slipage between the discs of slip clutch 50 and reduces the speed of tumbling drum 24. The speed reduction has the effect of reinitiating desirable tumbling action within the drum. With desirable tumbling action once again established, the light beam falls upon LDR 90 to reduce its resistance. Maximum voltage potential is then applied across transistor 158 to provide maximum energization of slip clutch 50.

When the dryer is first turned on, the ports 86 and 88 of drum 24 may not be aligned with light source 84 and LDR 90. Consequently, no light will strike the LDR 90 to initiate control circuit energization and drum rotation. Therefore a start bypass conductor 174 around LDR 90 extends from conductor 150' to conductor 154 to initially trigger transistors 158 and 164. A timer controlled switch 176 in bypass conductor 174 is closed when the dryer is turned on and is opened a predetermined period of time later.

FIG. illustrates a hypothetical plot of drum speed vs. time for a dryer utilizing the present invention. From zero time to approximately one minute after dryer turn on the dryer operates with switch 176 closed. During this initial period, the clutch coil 124 is energized a maximum amount and the drum 24 is rotated at maximum speed. Thereafter the switch 176 is opened by timer 114 and drum speed is regulated in response to the amount of light striking LDR 90. At the end of a drying cycle, the timer 114 opens switch 94 and terminates dryer operation. The drum speed variance exhibited during the period when LDR 90 functions to control the clutch coil 124 effectively maintains desirable tumbling action within the drum.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A domestic clothes dryer comprising: a cylindrical tumbling drum supported within the dryer for rotation about a substantially horizontal axis; said tumbling drum having an interior space; a closeable access opening through which damp clothing can be passed into said interior space; air inlet means to said interior space; air outlet means from said interior space; air heating means including a fan to cause ambient air to enter the dryer through said inlet means, to be heated, to flow through said interior space and to exit through said outlet means; a motor powered variable speed drive means for rotating said tumbling drum; a light source located adjacent one end of said tumbling drum; a photosensitive device located adjacent the other end of said tumbling drum; a plurality of ports in a circular pattern in one end of said tumbling drum; a plurality of ports in a circular pattern in the other end of said tumbling drum; both said circular patterns being concentric with respect to the rotational axis of said tumbling drum; said ports in opposite ends of said drum being aligned with respect to a light beam extending between said light source and said photosensitive device whereby a substantially continuous beam of light may extend through said drum while it is rotating; circuit control means coactive with said photosensitive device and said variable speed drive means to vary the drums rotational speed in response to energization of said photosensitive device by said light source and whereby the speed of said tumbling drum will be reduced from a predetermined maximum speed when said light beam is interrupted by damp clothes plastered against the tumbling drum to initiate desirable tumbling action of clothes within the drum.

2. A domestic clothes dryer comprising: a cylindrical tumbling drum supported within the dryer for rotation about a substantially horizontal axis; said tumbling drum having an interior space; a closeable access opening through which damp clothes can be passed into said interior space; air inlet means to said interior space; air outlet means from said interior space; air heating means including a fan to cause ambient air to enter the dryer through said inlet means, to be heated, to flow through said interior space and to exit through said outlet means; a motor powered variable speed magnetic slip clutch for rotating said tumbling drum; a light source located adjacent one end of said tumbling drum; a photosensitive device located adjacent the other end of said tumbling drum; a plurality of ports in a circular pattern in one end of said tumbling drum; a plurality of ports in a circular pattern in the other end of said tumbling drum; both said circular patterns being concentric with respect to the rotational axis of said tumbling drum; said ports in opposite ends of said drum being aligned with respect to a light beam extending between said light source and said photosensitive device whereby a substantially continuous beam of light may extend through said drum while it is rotating; circuit control means coactive with said photosensitive device and said variable speed magnetic slip clutch to vary the drums rotational speed in response to energization of said photosensitive device by said light source and whereby the speed of said tumbling drum will be reduced from a predetermined maximum speed when said light beam is interrupted by damp clothes plastered against said tumbling drum to initiate a desirable tumbling action of clothes within the drum.

3. A domestic clothes dryer comprising: a cylindrical tumbling drum supported within the dryer for rotation about a substantially horizontal axis; said tumbling drum having an interior space; a closeable access opening through which damp clothing can be passed into said interior space; air inlet means to said interior space; air outlet means from said interior space; air heating means including a fan to cause ambient air to enter the dryer through said inlet means, to be heated, to flow through said interior space and to exit through said outlet means; a motor powered variable speed magnetic slip clutch for rotating said tumbling drum; a light source located adjacent one end of said tumbling drum; a photosensitive device located adjacent the other end of said tumbling drum; a plurality of ports in a circular pattern in one end of said tumbling drum; a plurality of ports in a circular pattern in the other end of said tumbling drum; both said circular patterns being concentric with respect to the rotational axis of said tumbling drum; said ports in opposite ends of said drum being aligned with respect to a light beam extending between said light source and said photosensitive device whereby a substantially continuous beam of light may extend through said drum while it is rotating; said photosensitive device being a light dependent resistor having high dark resistance and decreasing resistance in response to increasing light intensity; crcuit control means coactive with said light dependent resistor and said variable speed magnetic slip clutch to vary the drums rotational speed in response to energization of said light dependent resistor by said light source and whereby the speed of said tumbling drum will be reduced from a predetermined maximum speed when said light beam is interrupted by damp clothes plastered against said tumbling drum to initiate desired tumbling action of clothes within the drum.

4. A domestic clothes dryer comprising: a cylindrical tumbling drum supported within the dryer for rotation about a substantially horizontal axis; said tumbling drum having an interior space; a closeable access opening through which damp clothes can be passed into said interior space; air inlet means to said interior space; air outlet means from said interior space; air heating means including a fan to cause ambient air to enter the dryer through said inlet means, to be heated, to flow through said interior space, and to exit through said outlet means; a motor driven variable speed drive means for rotating said tumbling drurn; a light source located adjacent one end of said tumbling drum; a photosensitive device located adjacent the other end of said tumbling drum; light transmitting means on the ends of said drum to permit passage of a substantially continuous beam of light through said interior space of said rotatable tumbling drum; circuit control means coactive with said photosensitive device and said variable speed drive means to vary the drums rotational speed in response to energization of said photosensitive device by said light source and whereby the speed of said tumbling drum will be reduced from a predetermined maximum when said light beam is interrupted by damp clothes plastered against said tumbling drum to initiate desirable tumbling action of clothes within the drum.

5. In a domestic clothes dryer of the type including a substantially horizontal, rotatable tumbling drum which has an interior space for the placement of damp clothes to be dried; air heating means including a fan to cause heated air to flow through said interior space of said tumbling drum; the improvement comprising: a motor powered variable speed drive means for rotating said tumbling drum; light transmitting means in the ends of said drum to permit the passage of a substantially continuous beam of light through said interior space; a light source and a photosensitive device located to permit a light beam therebetween to pass through said light transmitting means and said interior space while the tumbling drum is rotating; circuit control means coactive with said photosensitive device and said variable speed drive means to vary the drums rotational speed in response to ener- References Cited UNITED STATES PATENTS 1/1963 Horecky 34-52X 8/1966 Sones et al 34-52X CARROLL B. DORITY, IR., Primary Examiner 

